Gentrification

Gentrification is a process of renovating deteriorated urban neighborhoods by means of the influx of more affluent residents. Gentrification shifts a neighborhood's racial/ethnic composition and average household income by developing new, more expensive housing, businesses, and improved resources, and real estate development can lead to lowered crime rates, increased attraction of business, redevelopment of warehouses and abandoned buildings into loft apartments, and improved material quality. However, gentrification can lead to the displacement of lower-income families and local businesss and a rise in property values and rental costs. Most gentrifiers are affluent professionals such as highly-educated women, adventurous artists, and newcoming gays.

White flight
In the United States, white flight from the cities during the 1950s and 1960s led to formerly upper- or middle-class communities such as Yonkers and The Bronx in New York, Compton in California, and Newark in New Jersey becoming impoverished and crime-ridden cities. The rise of the suburbs, caused by the influx of returning World War II veterans in the late 1940s and early 1950s, led to many white residents leaving the cities, a process hastened by the process of "blockbusting", in which real estate agents encouraged whites to sell their homes at high prices rather than have their homes decrease in value due to the arrival of poorer African-American and Hispanic residents.

Urban decay
The Great Migration of poor blacks from the American South into cities across the country to work as laborers led to the arrival of working-class blacks in several major cities. Their arrival in certain neighborhoods decreased property values, and many white residents sold their homes and flocked to the suburbs to live in comfort. Both white flight and the construction of highways over certain neighborhoods led to a decrease in property value, and these values were affordable to the new African-American workforce and to immigrants from Hispanic countries, primarily Puerto Rico. For example, Newark's white population decreased from 363,000 people in 1950 to 46,000 in 1967, and Newark had a black majority by 1966, a faster turnover than most northern cities had experienced. Southern blacks and Puerto Ricans moved to Newark to become industrial workers just as industrial jobs were decreasing sharply, and many of the migrants left poverty to find more poverty. The 1967 Newark riots destroyed the city's prosperity, and the white community left with the industrial jobs.

New York City experienced a similar decline during the 1960s and 1970s, with most of the Italians leaving Harlem, the Jews leaving Brooklyn and The Bronx, and the Irish leaving Queens as the neighborhoods were overrun by an influx of poor African-American and Puerto Rican laborers. The construction of the Cross-Bronx Expressway through the Bronx led to the destruction of swathes of buildings and the decline of the South Bronx, which became a Puerto Rican ghetto. During the 1970s, The Bronx and parts of Brooklyn were devastated by frequent arson attacks, with several buildings being boarded-up or reduced to vacant lots. Drugs, homelessness, poverty, and crime became rampant, and the saying "The Bronx is Burning" became popular in The Bronx during the late 1970s, while Bedford-Stuyvesant became known as "Bed-Stuy, do-or-die" due to skyrocketing crime and murder rates. New York City was devastated by white flight and urban decay, and even the famous district of Times Square became infected by porn shops and drug deals.